1. Field of the Invention
This invention relates to thermo-electric generators of the kind making use of beta alumina ceramic through which sodium is circulated to produce an electric potential between the two surfaces of the ceramic.
2. Prior Art
One form of such a device is described in U.S. Pat. No. 3,458,356, in which specification, one face of a disc of beta alumina ceramic is exposed to sodium vapour and the opposite face is exposed to a region of lower pressure and lower temperature. The sodium migrates through the ceramic material generating an electric potential between porous conductive layers on the faces of the ceramic. To provide a continuously-operating thermo-electric generator, the sodium passing through the ceramic is circulated back to the other face and heated.
A thermo-electric generator of this type would be particularly attractive for making use of a high temperature heat source; the thermo-electric generator could be used in series with a steam turbine, the thermo-electric generator working between some higher temperature and the maximum temperature of the steam turbine to thereby increase the overall thermal efficiency of electricity generation. Devices such as have been proposed heretofore however have not been suitable for large scale operation. One of the reasons for this is the problem of effecting a high temperature sodium resistant seal between the ceramic electrolyte and the sodium container, such a seal being necessary in constructions such as have been proposed heretofore.